System for selective laser assisted plating

Abstract

A method directed to a system for splitting, imaging and focusing a pulsing laser beam, such as from an excimer laser, onto a workpiece to improve the subsequent metal plating of such workpiece. A preferred technique of laser assisted plating is a system for laser ablating a plurality of contact areas on electrical terminals, where the areas are covered by ablatable resist. The preferred system comprises a carrier strip having a plurality of electrical terminals mounted thereon; a pulsed laser for directing radiation at the carrier strip; a hologram mounted in the radiation path between the laser and the carrier strip for splitting the radiation from the laser into a plurality of radiation beams directed towards the plurality of contact areas; and mechanism for synchronizing the movement of the carrier strip with the pulsing of the laser so that a respective one of the plurality of outgoing beams ablates the resist over a respective one of the contacts as the contact areas move past the hologram.

I claim: 
     
       1. A method of improving a surface of a metallic workpiece for subsequent selective metal plating thereof, where at least one workpiece is joined to a carrier strip, comprising the steps of a) positioning a pulsed laser, operating at a predetermined pulsing rate, near said workpiece,   b) preparing a hologram capable of splitting a radiation beam of said pulsed laser,   c) placing said hologram intermediate said pulsed laser and said workpiece,   d) directing the radiation beam of said pulsed laser towards said hologram and said carrier strip, where said hologram is within a radiation path between said pulsed laser and said carrier strip,   e) splitting the radiation beam at said hologram into a plurality of radiation beams directed towards said metal workpiece, and   f) coordinating the movement of said carrier strip with the pulsing rate of said laser so that a respective one of said plurality of radiation beams affects at least one said metal workpiece as said metal workpiece moves past said hologram.   
     
     
       2. The method according to claim 1 wherein said plurality of radiation beams from said hologram are directed to multiple images on a single workpiece. 
     
     
       3. The method according to claim 1 wherein said laser is a pulsed laser operating at a wavelength between about 248 to 360 nm, and that the radiation beams thereof are capable of ablating areas of plating resist from said metal workpiece. 
     
     
       4. The method according to claim 1 including the step of correcting the angular relationship of the hologram with respect to a reference angle of the said radiation path to accommodate reconstruction of said hologram at the operating wavelength of said pulsed laser. 
     
     
       5. The method according to claim 3 wherein said hologram is prepared from a material that exhibits a high damage threshold within said laser operating wavelength. 
     
     
       6. The method according to claim 5 wherein said material is a dichromated gelatin.